1. Field of the Invention
The present invention relates to a protective device which protects various communication devices, for example, connected to a power line and a communication wire such as a telephone line, from a rapid increase of current due to a rapid increase of voltage in the communication wire and the power line induced by thunder, and relates to a communication device with the above protective device mounted thereon.
2. Description of the Related Art
Various communication devices used by connecting themselves to a communication wire such as a telephone line or used by connecting themselves to a power line for receiving power, for example, to a commercial AC (alternating current) outlet, are used in order to establish a connection of a communication line. For example, there are a telephone, a facsimile machine, a TA (Terminal Adapter), a personal computer with a communication function built in, and so on.
Various protective devices are provided in order to protect these communication devices from a rapid increase of current (serge current) caused by a rapid increase of voltage induced in a communication wire and a power line by thunder. The protective device is to prevent the surge current flowing into a communication device, and when an excessive surge current flows in a power line and a fuse in the protective device is broken, that one having an indicator showing that a fuse has been broken is provided.
More concretely, the protective device is provided with a LED (Light Emitting Diode) for indicating a current-carrying state. When a fuse in the protective device is broken, the LED goes out. This notifies a user that an excessive surge current flows in a power line, thereby blowing the fuse in the protective device. The shutoff of the LED when the fuse is broken can inform a user that the communication device can be protected from the surge current caused by thunder, thereby inducing a user to exchange a fuse in the protective device with a new one.
As mentioned above, when an excessive surge current occurs, thereby breaking a fuse connected to a power line, the protective device for protecting a communication device from the surge current caused by thunder notifies a user that the fuse has been broken, in a way of shutting off the LED for indicating a current-carrying state.
In the case of a surge current within the range of normal operation of the protective device, not such a large surge current as to break a fuse of the protective device, it is impossible to notify a user through the protective device that the communication device is protected. Therefore, a user may worry about whether the protective device operates normally or not.
As long as such an excessive surge current as to break a fuse of the protective device does not flow, it is impossible to show the validity of the protective device which protects a communication device from thunder, to a user. Therefore, the protective device cannot attain reliability and satisfaction of a user to the full.
Taking the above into consideration, the present invention aims to provide a protective device capable of notifying the state of protecting a communication device connected to a communication wire and a power line from a rapid increase of current, and a communication device with the above protective device mounted thereon.
In order to solve the above problem, a protective device according to a first aspect of the present invention is a protective device which connects a communication device to a communication wire and a power line and protects the communication device from a rapidly increasing current due to a rapid increase of voltage induced in the communication wire and/or the power line, comprising:
informing means for informing the operation of a protective function when the protective function operates due to a rapid increase of current;
current change detecting means for detecting a rapid increase of current which occurs in the communication wire and/or the power line; and
control means for controlling the operation of the informing means based on the detection output from the current change detecting means.
According to the protective device of the first aspect of the present invention, the current change detecting means detects a rapid increase of current caused by a rapid increase of voltage which occurs in a communication wire and/or a power line connected to a communication device. When the current change detecting means detects a rapid increase of current, the control means controls the informing means to operate depending on the detection output, thereby informing a user that a protective function operates.
Thus, when the protective device operates to protect a communication device if there occurs a rapid increase of current flowing in the communication wire or the power line, due to thunder, even not so large as to break a fuse of the protective device and to break the protective device, the protective device of the present invention can notify a user of that.
A protective device according to a second aspect of the present invention is the protective device of the first aspect, wherein
the current detecting means has a toroidal coil and the communication wire and the power line corresponding to portions where occurrence of a rapid increase of current is to be detected are passed through a core of the toroidal coil.
According to the protective device of the second aspect of the present invention, the current change detecting means is formed by so-called a toroidal coil (ring coil) made by wrapping a wire around a ring core portion, and the communication wire and the power line corresponding to the portions where occurrence of a rapid increase of current is to be detected are passed through the ring core portion of the toroidal coil.
Thus, it is possible to detect a rapid increase of current in the predetermined portions sensitively and surely and inform a user that a protective function operates or has operated, easily.
A protective device of a third aspect of the present invention is the protective device of the first aspect, wherein
the informing means is formed by using a light-emitting element, and
the control means controls the light-emitting element to light up for a constant hour when a rapid increase of current is detected by the current change detecting means.
According to the protective device of the third aspect of the present invention, the informing means is formed by a light-emitting element, for example, LED and so on, and when the current change detecting means detects a rapid increase of current, the light-emitting element as the informing means is controlled to light up for a constant hour by the control means.
Thus, when a rapid increase of current occurs and the protective function operates, the light-emitting element lights up for a constant hour, thereby informing a user that the protective function is operating to protect the communication device, surely and easily.
A protective device of a forth aspect of the present invention is the protective device of the first aspect, wherein
the informing means is formed by using a light-emitting element,
instruction receiving means for receiving a shutoff instruction from a user is provided, and
the control means controls the light-emitting element to light up until receiving the shutoff instruction through the instruction receiving means when a rapid increase of current is detected by the current detecting means.
According to the protective device of the forth aspect of the present invention, the informing means is formed by a light-emitting element, for example, LED and so on, and when the current change detecting means detects a rapid increase of current, the light-emitting element as the informing means is controlled by the control means to light up and to keep lighting up until receiving a shutoff instruction of the LED through the instruction receiving means.
Thus, when a rapid increase of current occurs and the protective function operates, the light-emitting element can be kept lighting up until receiving an instruction, thereby informing a user that the protective function operates to protect a communication device, surely and clearly.
A protective device of a fifth aspect the present invention is the protective device of the first aspect, further comprising:
count means for counting the detection times of rapid increase of current by the current change detecting means; and
count value output means for supplying count value by the count means.
According to the protective device of the fifth aspect of the present invention, when the current change detecting means detects a rapid increase of current, the count means starts counting to count the detection times of rapid increase of current. The count value by the count means is provided to a user through the count value output means, for example, LCD, a rotating count display unit mechanically formed, or the like. Thus, a user can correctly know how many times a rapid increase of current occurs, and he or she can know the validity of the protective device surely.